Blasting-cap



A. 1. STRANE.

BLASTING CAP.

APPLICATION FILED APR. 21. 1920.

Patented Nov. 9, 1920.

ARCHIBALD J. STRANE, OF TAMAQA, PENNSYLVANIA, ASSIGNOR TO ATLAS POWDER COMPANY, OF PHILADELPHIA, PENNSYL VANIA, A CORPORATION OF DELAWARE.

BLASTING-CAP.

Application led April 21,

T0 @ZZ 'whom izL may concern.'

Be it knoxvn that I, ARCHIBALD J. STRANE, a citizen of the United States of America., residing at Tamaqua, in the county of Schuylkill and State of Pennsylvania, have invented certain new and useful Improvements in Blasting-Caps, of which the following is a specification.

T his invention relates to blasting caps or detonators and more particularly to means for preventing the usual deleterious effect of moisture absorption by said blasting caps.

In commercial and in some military blasting operations the main explosive charges are detonated by means of primers which are known as blasting caps or detonators.7 The common type of commercial primer consists of a small metal capsule partly filled with a primary explosive com-- position which is best adapted for the efiicient detonation of the particular explosive Which makes up the main charge with which the primer is to be used. The capsules are not completely filled with the primary eX- plosive composition but, as a rule, are only about half filled, thus leaving an open space for the reception of the end of the fuse. The fuse is usually of a size to fit snugly within the capsule and after the fuse is inserted as far as possible the metal of the capsule is crimped to force it into engagement with the fuse and thereby prevent the accidental separation of the tWO.

The explosive composition used in most blasting caps or detonators is very easily effected by the absorption of moisture from the atmosphere and this may result in a complete failure of the blasting cap or detonator to respond to the burning of the fuse. This condition produces what, in min` ing, is known as a misfire7 which is not onlv costly but exceedingly dangerous as Well.

Miners endeavor to eliminate these misfires by using great care to keep the blasting caps in a dry place until used or else dry them out before they are used. The former is mostly relied upon but frequently difficulty arises because moisture absorption has taken place unknown to the operators. lven in the latter case the blasting caps are in an unreliable condition by the time they are fired. due to the extremely humid atmosphere at the place of use.

For the above reasons it is highly desir- Specfication of Letters Patent.

Patented Nov. 9, 1920.

1920. serial No. 375,518.

able to provide means for individually Water-proofing each blasting cap to render it absolutely impervious to moisture and dependable for use, even though it may have been subjected to a very humid atmosphere for either a short or a long period.

It is also desirable to provide a closure of the character indicated of such a nature that it may be easily and quickly removed when the fuse is to be inserted in the blasting cap or may even be pushed down into the capsule by the end of the fuse, While at the same time it will not prevent the efficient ignition of the primer composition Wit-hin the cap, from the fuse.

The figure shown in the accompanying drawing is a magnified sectional view of a blasting cap constructed in accordance With the invention.

Referring to the drawing, 5 designates the metallic shell or capsule and 6 the primer composition therein. As before stated this primer composition only partly fills the capsule. thereby leaving an open space 7 into which the end of the fuse may be inserted. To hermetically seal the capsule and protect the primer composition 6 from moisture absorption the open end of the capsule is closed by a film or disk of impervious, frangible and infiammable material. Preferably this film or disk is provided by dipping the end of the capsule in a more or less viscous solution of nitrocellulose in any suitable solvent, the evaporation of the excess solvent leaving a collodion film or disk having the characteristics aforesaid. Such a disk is impervious to moisture, is breakable under the thrust of a fuse; a'. e. it may be easily broken by thrusting the end of the fuse thereagainst and if a part of it is pushed down into the blasting cap and lies between the end of the fuse and the primer composition it Will not, because of its inflammable nature interfere With the ignition of said primer composition.

A closure of this nature possesses a further advantage in that it does not project beyond the sides of the blasting cap and consequently does not interfere With present methods of packing such blasting caps for shipment.

It is to be understood that the invention is not limited to the use of the particular material named for forming the closure disk, since any materia-l found suitable for the purpose may be employed and the invention includes Within its purview whatever adaptations thereof fairly come within either the terms or the spirit of the appended claims.

Having described my invention, what I claim is- 1. A blasting cap having its open end hermetically sealed by a closure of impervious material that is frangible under the thrust of a fuse and inflammable under the spit of a fuse, said blasting cap containing an explosive material which only'partially lls the said cap and lies in spaced relation to said web.

2. As an article of manufacture, a blasting cap comprising a shell closed at one end and open at the other and having a partial filling of explosive detonating material therein and having a part ofits interior empty for the reception of the end of a iexible fuse, and a closure for the open end of the shell consisting solely of a collodion disk that is breakable under the thrust of a fuse and inflammable under the spit of a fuse.

In testimony whereof I affix my signature `in the presence of two Witnesses.

ARCHIBALD J. STRANE,

Witnesses:

JAMES H. SMITH, Jr.,

HOWARD'N. FINN. 

